<!DOCTYPE html>
<html lang="zh-CN">
<!--lang==language 指定语言为中文-->

<head lang="zh-CN">
    <title>Days Gone</title>
    <link rel="icon" href="./media_resourcing/title_logo.ico" type="images/x-ico" />
    <!--设置标题网页logo-->
    <meta charset="UTF-8">
    <style>
        .father {
            width: 400px;
            height: 400px;
            background-color: blue;
            border: 1px solid transparent;
            /* 如果注释border这一行,就会引起sondiv的margin 100px失效*/
            /* padding : 1px 也行 */
            /* overflow: hidden; 最有效,无需改动盒子大小 */
        }
        
        .son {
            width: 200px;
            height: 200px;
            background-color: green;
            margin-top: 100px;
        }
    </style>
</head>

<body>
    <div class="father">
        <div class="son"></div>
    </div>
</body>

</html>